Water Content Detection Sensor System

ABSTRACT

A water content detection sensor includes a circuit member in which low resistance conductors  1,2  disposed in parallel to each other and a high resistance conductor  3  connecting end portions of the respective low resistance conductors, a carrier body  4  having a water-proof property and an insulating property, and a coating body  5  having a water-proof property and an insulating property, the circuit portion being disposed between the carrier body and the coating body. A plurality of exposure holes  6  are formed to the carrier body or the coating body so as to expose the low resistance conductors at plural portions, and when water content adheres between the exposure holes and the low resistance conductors are then short-circuited in a current conduction state, a current value is made larger than that before the adhesion of the water content. When a small current passes, it is judged that the circuit is normal, and on the other hand, a large current passes, it is judged that water is generated.

TECHNICAL FIELD

The present invention relates to a water content (or merely water)detection sensor.

BACKGROUND ART

Generally, there is known a water content detection sensor for detectingpresence or generation of water content or moisture at a time when thewater content or water adheres between electrodes and electric currentpasses (Such water content detection sensors are disclosed, for example,in Patent Literature 1, 2, 3.). Such water content detection sensors areutilized for automatic wipers of automobiles, diapers and so on.

Patent Literature 1: JP-63-290950 Patent Literature 2: JP-2000-19136Patent Literature 3: JP-2002-82080 DISCLOSURE OF THE INVENTION Problemsto be Solved by the Invention

In the water content detection sensor of the structure described in theabove prior art references, for example, under the presence of apotential difference between the electrodes, when an electric currentpasses upon adherence of the water content between the electrodes, asignal is generated by the detection of the current and an output signalis then detected. In such structure, however, the performance of acircuit itself including the electrodes could not be judged, and it istherefore impossible to detect the generation or presence of the watercontent or water at the time of adhesion of the water content betweenthe electrodes because of no generation of any signal due to fault ofthe circuit such as electrodes.

Furthermore, a conventional water content detection sensor is alsoutilized for diapers for detecting urination or evacuation. In such acase, when it is desired to detect the urination through plural times,resistance values may be changed, which results in a cause of erroneousoperation of the detector.

Accordingly, the present invention was conceived in consideration of thecircumstances mentioned above and an object of the present invention isto provide a water content detection sensor capable of surely detectingthe presence of water content or water between electrodes.

Means for Solving the Problems

The above and other objects can be achieved according to the presentinvention by providing a water content detection sensor comprising: acircuit member in which low resistance conductors (1,2) disposed inparallel to each other and a high resistance conductor (3) connectingend portions of the respective low resistance conductors (1,2) so as toprovide a series of line; a carrier body (4) having a water-proofproperty and an insulating property; and a coating body (5) having awater-proof property and an insulating property, the circuit memberbeing disposed between the carrier body (4) and the coating body (5),wherein a plurality of exposure holes (6) are formed to the carrier body(4) or the coating body (5) so that the low resistance conductors (1,2)are exposed at plural portions, and when water content (W) adheresbetween the exposure holes (6) and the low resistance conductors (1,2)are then short-circuited in a current conduction state, a current valueis made larger than that before the water content (W) adheres.

In a preferred embodiment of the above aspect of the present invention,the low resistance conductors (1,2) and the high resistance conductor(3) may be formed by being printed on the carrier body (4) in form offilm and the coating body (5) is printed thereon.

Portions of the low resistance conductors (1,2) corresponding to theexposure holes (6) may be formed as enlarged portions (6 a) each havingan area larger than that of the exposure hole (6)

Extending portions (1 a,2 a) of the low resistance conductors (1,2) andthe exposure holes (6) may be formed to portions at which the watercontent (W) is likely concentrated.

The carrier body (4) and the coating body (5) may be formed with throughholes (9 a,9 b) through which water passes.

The low resistance conductors and the high resistance conductor may beprinted with conductive ink including conductive carbon.

It may be desired that the printing ink of the low resistance conductorincludes the conductive carbon of an amount larger than that included inthe printing ink of the high resistance conductor.

The coating body or the carrier body, to which the exposure holes areformed, may be formed as a lamination member composed of printing inklayers, and at least one layer of the lamination member is formed ofurine resist ink.

It may be desired that at least one of the layers of the laminationmember disposed between the urine resist ink layer and the low and highresistance conductors is formed of solvent resist ink. The urine resistink may be urethane combined ink of polyester polyal and isocyanate orUV hardened resin ink. The solvent resist ink may be a polyester resinink.

The low and high resistance conductors may be formed by being printedwith conductive ink including only conductive carbon as conductivesubstance.

EFFECTS OF THE INVENTION

According to the present invention of the characters mentioned above,when the water (W) or like adheres between the exposure holes (6) in thecurrent conduction state and the low resistance conductors (1,2)extending in parallel is then short-circuited, the current passingthrough the circuit increases in comparison with the case before thewater (W) adhesion, so that the water content detection sensor cansurely detect the water content (W) by observing the state of thecircuit.

By printing the low and high resistance conductors on the film shapedcarrier body or coating body, the water content detection sensor can bemade thin, and hence, it can be disposed in a narrow portion orirregular surface portion.

By portions of the low resistance conductors corresponding to theexposure holes are formed as enlarged portions each having an arealarger than that of the exposure hole, even in the case of fine lowresistance conductors, the water content detection sensor having highprecision can be provided.

In addition, since extending portions of the low resistance conductorsand the exposure holes are formed to portions at which the water contentis likely concentrated, the sensitivity of the water content detectionsensor can be improved.

In the embodiment in which the through holes (9 a,9 b) are formed to thecarrier body and the coating body, even in the case where the waterexists on the side opposite to the exposure holes (6), the water content(W) can be exactly detected.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 is a front view of a water content detection sensor according toa first embodiment of the present invention;

FIG. 2 is a rear view of the water content detection sensor of the firstembodiment;

FIG. 3 is a plan view of a circuit member of the water content detectionsensor;

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1;

FIG. 5 is a plan view showing a circuit member of a water contentdetection sensor according to a second embodiment of the presentinvention;

FIG. 6 is a plan view showing a circuit member of a water contentdetection sensor according to a third embodiment of the presentinvention;

FIG. 7 is a sectional view, like that of FIG. 4, of a water contentdetection sensor according to a fourth embodiment of the presentinvention.

EXPLANATION OF REFERENCE NUMERAL

1, 2 . . . low resistance conductor, 1 a, 2 a . . . extension portions 3. . . high resistance conductors 4 . . . carrier body, 5 . . . coatingbody, 6 . . . exposure hole, 6 a . . . enlarged portions 9 a, 9 b . . .water passing holes 9 a, W . . . water

BEST MODE FOR CARRYING OUT THE INVENTION

Hereunder, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings.

First Embodiment

As shown in FIGS. 1 to 4, a water content (or merely water) detectionsensor of this embodiment is provided with a circuit member includinglow resistance conductors 1, 2 extending in parallel and a highresistance conductor 3 connecting both ends of the low resistanceconductors 1 and 2 so as to provide a series of line. The circuit memberis interposed between a carrier or carrier body 4 and a coating body 5both having water-proof property and insulating property, and thecoating body 5 is formed with a plurality of holes as exposure holes 6through which the low resistance conductors are exposed. The exposureholes 6 may be formed to the carrier body 4.

The carrier body or carrier 4 is formed into a bendable belt-shape andadapted to carry the entire structure of the water content detectionsensor. The carrier body 4 has a water-proof property so as not to passthe water content and also has an electrically insulating property. Inaddition, it is desirable for the carrier body 4 to be formed to betransparent for the easy observation of the condition of the circuitmember. The carrier body 4 is formed from a biaxially oriented filmformed of polypropylene, polyethylene, polyvinyl-chloride, polyester,polyamide, polyimide, polycarbonate, polystyrene or like. It is alsodesirable for the carrier body 4 to have a thickness of 30 to 300 μm or,more preferably, 50 to 100 μm.

The circuit member includes the plural low resistance conductors 1 and2, which extend in parallel along both the side edges of the belt-shapedfilm forming the carrier body 4. The low resistance conductors 1 and 2are formed by printing the carrier body 4 with electrically conductiveink.

The conductive ink is formed by kneading binder, conductive metal powderand another filler, and as the binder, there may be used a polyvinylchloride group resin, a polyacryl group resin, an epoxy group resin, apolyester group resin, polyacrylic urethane group resin, a polyolefingroup resin, a urethane group resin, phenol or like resin.

As the conductive metal powder, there may be used silver, gold, copper,nickel, aluminium, conductive carbon or like.

The filler includes a viscosity controlling agent, a dispersing agentand the like.

The low resistance conductors 1 and 2 are formed by coating theconductive ink on the carrier body 4 in fine belt-like form throughscreen printing, direct gravure printing, flexographic printing or likeprinting process. Each of the low resistance conductors 1 and 2 isprinted with such conductive ink so as to have, for example, a width of1 mm, and a thickness of 10 μm, preferably, 5 to 30 μm. The resistancesof these low resistance conductors 1 and 2 are made to be 0 to 200 k Ω,preferably, less than 100 kΩ by regulating the content of the conductivemetal powder of the conductive ink. In this embodiment, it is set to beabout 100 kΩ.

On the other hand, the high resistance conductor 3 in the circuit memberis formed by being printed with the conductive ink of the compositionsubstantially the same as that of the low resistance conductor 1 (2).However, less amount of the conductive metal powder is contained in theconductive ink, and as a result, the resistance value of the highresistance conductor 3 is set to be larger than that of the lowresistance conductor 1 (2), for example, to several MΩ. In addition, inorder to easily distinguish from the low resistance conductors 1 and 2,the high resistance conductor 3 is formed to have a fine shape havingthickness of, for example, 0.5 mm. Furthermore, the high resistanceconductor 3 extends, from one end of one of the low resistanceconductors 1, to the other end along this low resistance conductor 1,then to other one end of the other low resistance conductor 2 andfurther toward one end of this low resistance conductor 2 therealong. Asa result, the high and low resistance conductors 3, 1 and 2 areconnected in form of a series of line on the carrier body 4 as oneconductor, and a potential difference is caused between the rear endportions of the low resistance conductors 1 and 2 so that the electriccurrent of a constant rate passes. It is desirable for the highresistance conductor 3 to have a resistance value of 1 to 10 MΩ,preferably of 2 to 6 MΩ.

Lead wires 7 and 8 are connected to the other ends of the two lowresistance conductors 1 and 2, respectively. These lead wires 7 and 8are also formed by being printed on the carrier body 4 with theconductive ink, which is the same as or similar to that for the lowresistance conductors 1 and 2.

The low resistance conductors 1 and 2 have extensions 1 a and 2 a to thefront end portion of the carrier 4, for example, on which the watercontent is likely concentrated. More specifically, one ends of therespective low resistance conductors 1 and 2 extend, in a bend form, tothe opposing side low resistance conductors 2 and 1 so as to cross thecarrier body 4. Further, the high resistance conductor 3 is also bentand extend as like as the low resistance conductors 1 and 2.

The coating body 5 is coated on the surface of the carrier body 4 fromthe upper portion of the circuit member so as to insulate the circuitmember together with the carrier body 4. The coating body is formed ofthe printing ink.

The printing ink is formed by kneading a binder, pigment and otherfillers.

As the binder, there may be used a polyvinyl chloride group resin,polyacrylic group resin, epoxy group resin, polyester group resin,polyacrylic urethane group resin, polyolefin group resin, polyurethanegroup resin, or phenol group resin. The binder further formed throughurethane-coupling of polyester polyal and isocyanate or UV hardenedresin.

As the pigment, there may be used a white pigment, for example, for easyidentification from the circuit. Further, the filler may include aviscosity controlling agent, dispersing agent and the like.

Such printing ink is coated on the surface of the carrier above thecircuit member, through the screen printing, direct gravure printingprocess or like, with the lead wires 7 and 8 remaining uncoated, thusproviding the coating body 5. This coating (coated) body 5 serves asinsulating film and water-proof film.

A plurality of exposure holes 6 are formed on the coating body 5 atwhich the low resistance conductors 1 and 2 are exposed. These exposureholes 6 are formed at the same time as the printing time of the coatingbody 5. In the illustrated example, these exposure holes 6 are formed ata predetermined interval along the two low resistance conductors 1 and 2extending in parallel, and one or plural exposure holes 6 are alsoformed to the extending portions 1 a and 2 a. In the illustratedexample, each of the exposure holes 6 also has a circular shape, but itmay take elliptical shape, rectangular shape or like shape as occasiondemands.

Further, an enlarged portion 6 a having an area larger than the exposurehole 6 may be formed, as occasion demands, on the low resistanceconductor 1 (2) corresponding to the exposure hole 6. According to theformation of such enlarged portion 6 a, even if the exposure hole 6 isformed in a manner slightly offset, the low resistance conductors 1 and2 can be exposed properly. When water content or water W adheres so asto straddle on or bridge between the exposure holes 6 on the lowresistance conductors, electric current is short-circuited between thelow resistance conductors 1 and 2, and this current value is larger thanthe case of no short-circuited state, thus detecting the adhesion of thewater W.

The carrier body 4 is formed with water passing holes 9 a penetratingthe carrier 4. In the illustrated example, such water passing hole 9 isperforated into approximately rectangular shape between the lowresistance conductors 1 and 2 or between the extended portions 1 a and 1b, but it may be perforated as an aggregation of many perforations.Accordingly, even in the case where the water content W adheres on theside of the coating body 5, it passes through the water passing holes 9a and 9 b to the exposure hole side to thereby properly detect the watercontent W.

Hereunder, the functions of the water content detection sensor of thestructure mentioned above will be described.

The circuit member and the coating body 5 of the water content detectionsensor are printed, with different colors of inks, on the carrier body 4formed from a transparent film, so that the presence of disconnection(breaking of wire) of the circuit or presence of fault of the coatingbody 5 can be immediately visually observed, thus easily discriminatingthe performance of the water content detection sensor itself.

Incidentally, when the lead wires 7 and 8 are connected to a powersource, not shown, to thereby apply a voltage on the circuit member, thecurrent passes from one of the low resistance conductor 1 to the otherlow resistance conductor 2 through the high resistance conductor 3. Bydetecting this current, the performance of the water content detectionsensor can be judged.

The water content detection sensor is used in a manner that it is bondedon a vehicle body, a window glass or others of an automobile so that theexposure hole side is exposed outward, or it may be bonded to a diaper.

When the lead wires 7 and 8 are connected to the power source such asbattery so as to apply voltage to the circuit member, the current passesfrom one of the low resistance conductor 1 to the other low resistanceconductor 2 through the high resistance conductor 3. By detecting thiscurrent, it is judged whether the water content detection sensoroperates normally or not.

When the water content W of, for example, rainwater, adheres so as tostraddle the exposure hole 6 on the two low resistance conductors 1 and2, they are short-circuited and the current passes. This current islarger than that in the case of no short-circuited state, and hence, bydetecting this current value, the adhesion of the water content can bedetected. This detection is informed to a control section of theautomobile by transmitting a signal from the detection sensor and, then,the control section judges the fact of presence of rainfall and theninstructs so as to operate wipers. After the rainfall, the water contentof the rainwater is evaporated, the current value is decreased, and bydiscriminating this fact, the control section stops the operation of thewipers.

In the case of the diaper, when discharged urination adheres so as tobridge across the exposure hole 6 on the low resistance conductors 1 and2, the conductors are short-circuited and the electric current passestherebetween. By detecting this fact, the presence of the urination isinformed through an alarm, for example.

Second Embodiment

In this second embodiment, as shown in FIG. 5, a high resistanceconductor 10 in the circuit member of the water content detection sensoris made short in comparison with that of the first embodiment.

Further, in this second embodiment, the same reference numerals areadded to members or elements corresponding to those in the firstembodiment and duplicated explanation is omitted herein.

Third Embodiment

In this third embodiment, as shown in FIG. 6, a high resistanceconductor 11 in the circuit portion of the water content detectionsensor is made further short in comparison with those of the first andsecond embodiments so as to extend linearly between two low resistanceconductors 1 and 2.

Further, in third embodiment, the same reference numerals are added tomembers or elements corresponding to those in the first or secondembodiment and duplicated explanation is omitted herein.

Fourth Embodiment

In a water content detection sensor of this fourth embodiment, as shownin FIG. 7, the coating body 5 formed to the exposure hole 6 is formed asa lamination member of a printed ink layer. More specifically, thelamination member of the coating body includes three printing ink layerssuch that a first solvent resist ink layer 5 a is printed on the low andhigh resistance conductors 1, 2 and 3 of the circuit member of thesurface of the carrier body 4, an urine resist ink layer 5 b is printedon the first layer 5 a and a second solvent resist ink layer 5 c isprinted further on the urine resist ink layer 5 b. In the printingoperations of the respective layers, the exposure holes 6 aresimultaneously formed as non-printed portion.

Polyester resin ink will be used as the solvent resist ink, and as theurine resist ink, there will be used urethane combined ink of polyesterpolyal and isocyanate, or UV hardened resin ink.

In the case of application of the water content detection sensor to thediaper, since the low and high resistance conductors 1, 2 and 3 areprotected by the coating body 5 consisting of the multi-layers of theprinting ink layers 5 a to 5 c, the intrusion of the urination from theurine resist ink layer 5 b into the low and high resistance conductors1, 2 and 3 can be prevented. Accordingly, the low and high resistanceconductors at the circuit member can be also prevented from changing inthe resistance values thereof. As a result, urination can be properlydetected in a plurality of times and the diaper can be used for theplural urinations. The invasion of the solvent component of the urineresist ink layer 5 b into the circuit member can be shut off by thefirst solvent resist ink layer 5 a, and the invasion on the sideopposite to the circuit portion can be also shut off by the secondsolvent resist ink layer 5 c.

Further, in this fourth embodiment, the same reference numerals areadded to members or elements corresponding to those in the first tothird embodiment and duplicated explanation is omitted herein.

Fifth Embodiment

In the water content detection sensor of the fifth embodiment, the lowand high resistance conductors 1, 2 and 3 in the first to fourthembodiments is printed with a conductive ink including only conductivecarbon as conductive substance. Accordingly, the low and high resistanceconductors 1, 2 and 3 exhibit high resistance against urine component,and hence, the variation of the resistance value can be suppressed. As aresult, in the case when such water content detection sensor is appliedto the diaper, the urination can be properly detected in plural times.

It is to be noted that the present invention is not limited to thedescribed embodiments and many other changes and modifications may bemade without departing from the scopes of the appended claims. Forexample, the exposure holes may be formed to the carrier body instead ofthe coating body. In addition, the coating body is formed with theprinting ink layers, but it may be formed with a film member as like asthe carrier body.

1: A water content detection sensor comprising: a circuit member inwhich low resistance conductors disposed in parallel to each other and ahigh resistance conductor connecting end portions of the respective lowresistance conductors; a carrier body having a water-proof property andan insulating property; and a coating body having a water-proof propertyand an insulating property, and the coating body, wherein a plurality ofexposure holes are formed to the carrier body or the coating body so asto expose the low resistance conductors at plural portions, and whenwater content adheres between the exposure holes and the low resistanceconductors are then short-circuited in a current conduction state, acurrent value is made larger than that before the water content adheres.2: The water detection sensor according to claim 1, wherein the lowresistance conductors and the high resistance conductor are formed bybeing printed on the carrier body in form of film and the coating bodyis printed thereon. 3: The water detection sensor according to claim 1,wherein portions of the low resistance conductors corresponding to theexposure holes are formed as enlarged portions each having an arealarger than that of the exposure hole. 4: The water content detectionsensor according to claim 1, wherein extending portions of the lowresistance conductors and the exposure holes are formed to portions atwhich the water content is likely concentrated. 5: The water contentdetection sensor according to claim 1, wherein the carrier body and thecoating body are formed with through holes through which water passes.6: The water content detection sensor according to claim 1, wherein thelow resistance conductors and the high resistance conductor are printedwith conductive ink including conductive carbon. 7: The water contentdetection sensor according to claim 6, wherein the printing ink of thelow resistance conductor includes the conductive carbon of an amountlarger than that included in the printing ink of the high resistanceconductor. 8: The water content detection sensor according to claim 1,wherein the coating body or the carrier body, to which the exposureholes are formed, is formed as a lamination member composed of printingink layers, and at least one layer of the lamination member is formed ofurine resist ink. 9: The water content detection sensor according toclaim 8, wherein at least one of layers of the lamination memberdisposed between the urine resist ink layer and the low and highresistance conductors is formed of solvent resist ink. 10: The watercontent detection sensor according to claim 9, wherein the solventresist ink is a polyester resin ink. 11: The water content detectionsensor according to claim 8, wherein the urine resist ink is urethanecombined ink of polyester polyal and isocyanate or UV hardened resinink. 12: The water content detection sensor according to claim 1,wherein the low and high resistance conductors are formed by beingprinted with conductive ink including only conductive carbon asconductive substance.